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marți, 18 septembrie 2012

Can Van Allen Belts Dictate Manned Spaceflight?

What Are Van Allen Belts?

Actually two distinct belts, the entire Van Allen radiation belt extends to 7 earth radii. The most dangerous belt is the inner belt, which lies 1.1-3.3 earth radii away. With high concentrations of energetic protons, energies would typically exceed 100 megavolts (MeV). An astronaut, much less any living thing, would be lucky to survive more than a few minutes.

Given the intense proton radiation, space flight without extreme amounts of armored protection on the space vehicle would almost be impossible. In 1958, with the first satellite Explorer I checking for cosmic rays, its Geiger-Müller tube registered off-scale with radiation while traveling through the inner belt. Subsequent measurements have registered over 400 MeV (400 million volts--can penetrate 143 mm lead). [(1968) The Radiation Belt and Magnetosphere]

Van Allen belts are a result of the collision of Earth's magnetic field with solar wind. Missions beyond low earth orbit leave the protection of the geomagnetic field, and transit the belts. Apollo missions were the first event where humans traveled through the Van Allen belts. Other known radiation hazards are cosmic rays, other Van Allen radiation, and solar flares. The astronauts only spent short periods of time flying through them in the heavily-shielded Command Module. ["Radiation Plan for the Apollo Lunar Mission"; AIAA paper 69-19]

NASA Knew The Dangers

Even though NASA was well aware of the danger of the Van Allen belts, they deliberately launched Apollo at specific times. They used lunar orbits which only crossed the edge of the belt to receive minimal radiation. Even on Skylab, 350m above earth, CNN reported astronauts saw flashes of light at this time. This radiation was seen through the walls of a heavily shielded space station, though shielded space suits, though closed eyes, and though their retinas.

Most of the other planets and moons all have intense magnetic fields, with belts just like earth’s Van Allen belt. It would be expected that most extra-solar planets (planets in other solar systems), would have the same fate.

The sun’s activity (solar maximum) has begun its 11-year cycle, and directly influences the behavior of the radiation belts. Almost anything can happen to the belts during a solar storm. Storms damage electronic components on spacecraft. Miniaturization of electronics has made satellites more vulnerable to radiation, as radiating ions could be as large as the circuit's charge.

Back in the 1950s, the radiation belts had few effects on people. But today, geomagnetic storms from a rogue belt can force short-circuits of earth’s sensitive electronics; and weather satellites, sensors, GPS, and television can be heavily damaged. The Van Allen belts are considered the cause of the Aurora Borealis. Here, particles striking the upper atmosphere fluoresce, and become visible.Nuclear Testing

There have been numerous high-altitude nuclear tests in space (1962), causing artificial radiation belts. Starfish Prime, one of those tests, created an artificial radiation belt that damaged one third of the satellites in low earth orbit. Solar cells, integrated circuits, and sensors can also be damaged by radiation from an artificial belt.

Several (known) locations of high altitude nuclear testing were at Johnston Island (Pacific), ARGUS (South Atlantic), and the Russian continent (Kazakhstan). The Soviets formally accused US of manufacturing the inner belt from nuclear testing. The US has also accused the USSR of creating the outer belt from nuclear testing. Strangely, it has been confirmed the belts have not weakened since a treaty banned all atmospheric testing.

Scientists believe the belts carry some protection against solar wind. This means a weakening of the belts could harm electronics and/or organisms. That means they may influence the earth's telluric current (a usually natural electric current flowing near the earth's surface). Scientists also believe that dissipating the artificial belts could influence the location of the magnetic poles on earth.

Future Space Travel

Future space travel must be done safely. Why hasn’t any additional manned trips been made to the moon in 40 years? All future programs to bring humans to the Moon again, and to Mars and beyond, have been cancelled indefinitely by NASA.

There’s likely many technical facts that have not been revealed to the general public. What happens when an astronaut gets radiation poisoning a few million miles away from home? Can space vehicles ever be shielded with enough lead to limit radiation exposure?

Maybe the Van Allen-type belt is universal—that is—one exists in every portion of the universe. Portions of the belt would be detrimental to any organic life form we’re aware of. Maybe the universe is devoid of any life as we know it, and we are the lone existing life form, in a very lonely place.

Many say our population is too big. All in a universe that may not have any more humans.